This application is based on and claims priority to Japanese Patent Application No. 2001-308553, filed Oct. 4, 2001, the entire content of which is hereby expressly incorporated by reference herein.
1. Field of the Invention
The present invention generally relates to a control system for a marine engine, and more particularly relates to an improved control system controlling a marine engine in response to signals from multiple sensors.
2. Description of Related Art
A marine drive, such as, for example, an outboard motor, drives a propulsion device such as, for example, a propellers, which is at least partly submerged when the watercraft on which it is installed is floating on a body of water. An engine used in a marine drive such as an outboard motor typically is either a two-cycle internal combustion engine or a four-cycle internal combustion engine.
An internal combustion engine for a marine drive typically has an intake device through which air is introduced into one or more combustion chambers. The air intake device typically incorporates a throttle valve or other mechanism to regulate an amount of air introduced into the combustion chambers during an intake portion of a cycle of the engine. The engine also employs a charge-forming device such as, for example, fuel injectors that spray fuel for combustion in the combustion chambers. As is well known, a ratio of the air amount relative to the fuel amount is called as an air-fuel ratio. The air-fuel ratio is one of the most significant values for control of the engine operation. Theoretically, a stoichiometric air-fuel ratio is selected as an ideal air-fuel ratio because, at this air-fuel ratio, the air-fuel charge or mixture can be completely burned in the combustion chambers.
In general, the engine can operate at an air-fuel ratio that varies from the stoichiometric air-fuel ratio by a limited amount. For example, an air-fuel ratio leaner than the stoichiometric air-fuel ratio may provide improved fuel economy. If, however, the air-fuel ratio of an engine operating at a stoichiometric air-fuel ratio is leaned, the output power (e.g., the torque) of the engine decreases. An engine for land vehicles is normally operated in a low speed range, in a low load range or in both low speed and low load ranges. Thus, a land vehicle engine is typically designed to operate at a lean air-fuel ratio under normal running conditions and to operate at the stoichiometric air-fuel ratio or at a richer air-fuel ratio when the engine load becomes high such as, for example, when the engine is accelerated to increase the speed of the land vehicle or to provide more output power.
On the other hand, unlike the land vehicle engine, a marine engine is normally or frequently operated at high speed, at high load or at high speed and high load. Since the fuel consumption of a land vehicle engine usually increases because of the use of the richer air-fuel ratio at high speeds and at high loads, control systems typically used by land vehicle engines are not practical for use with marine engines.
A need exists for a control system for a marine engine that can operate the engine at a lean air-fuel ratio as much as possible in a high speed range, a high load range or a combination of a high speed range and a high load range to decrease the fuel consumption of the marine engine.
One aspect of an embodiment in accordance with the present invention is an internal combustion engine for a marine drive that comprises an engine body. A first movable member (e.g., a piston) is movable relative to the engine body. The engine body and the movable member together define a combustion chamber. A second movable member is movable in response to movement of the first movable member. An air intake device introduces air to the combustion chamber. The air intake device incorporates an air regulation device (e.g., a throttle valve) that regulates an amount of the air. An actuator actuates the air regulation device. A fuel injector sprays fuel for combustion in the combustion chamber. A first sensor detects an intake pressure in the intake device. A second sensor is responsive to a state of the actuator or a state (e.g., a position) of the air regulation device. A third sensor is responsive to a speed of the second movable member. A control device controls an amount of the fuel relative to the amount of the air. The control device operates in first and second modes. In the first mode, the control device controls the amount of the fuel based upon a signal of the third sensor and a signal of the first sensor in a first operational range of the air regulation device in which the intake pressure is variable. In the second mode, the control device controls the amount of the fuel based upon the signal of the first sensor and a signal of the second sensor in a second operational range of the air regulation device in which the intake pressure is invariable.
Another aspect of an embodiment in accordance with the present invention is a control system for a marine engine. The engine has an air intake device to introduce air to a combustion chamber of the engine. The intake device incorporates an air regulator (e.g., a throttle valve) that regulates an amount of the air. A fuel injector sprays fuel for combustion in the combustion chamber. The control system comprises an actuator coupled to the air regulator. A first sensor detects an intake pressure in the intake device. A second sensor is responsive to a state of the actuator or a state (e.g., a position) of the air regulator. A third sensor is responsive to a speed of the engine. A control device controls an amount of the fuel relative to the amount of the air in two modes. In a first mode, the control device controls the amount of the fuel based upon a signal of the third sensor and a signal of the first sensor in a first operational range of the air regulator in which the intake pressure is variable. The control device controls the amount of the fuel based upon the signal of the first sensor and a signal of the second sensor in a second operational range of the air regulator in which the intake pressure is invariable.
A further aspect of an embodiment in accordance with the present invention is a control method for controlling a marine engine. The method comprises sensing an intake pressure of an air intake device, sensing a parameter responsive to a state (e.g., a position) of an air regulator of the intake device or a state of an actuator of the air regulator, sensing an engine speed of the engine, and controlling an amount of fuel injected by a fuel injector relative to an amount of air introduced through the intake device in first and second control modes. In the first control mode, the amount of fuel injected is controlled based upon the engine speed and the intake pressure in a first operational range of the air regulator in which the intake pressure is variable. In the second control mode, and the amount of the fuel injected is based upon the engine speed and the sensed parameter of the air regulator or actuator in a second operational range of the air regulation device in which the intake pressure is invariable.
Another aspect of an embodiment in accordance with the present invention is an engine control system for an internal combustion engine for a marine drive. The engine comprises at least one combustion chamber that receives air-fuel charges. The engine operates at a variable engine speed in response to ignition of the air-fuel charges. The engine further comprises an air intake device that introduces air to the combustion chamber. The air intake device incorporates an air regulator (e.g., a throttle valve) that regulates an amount of air introduced to the combustion chamber by the air intake device. A fuel injector introduces fuel to the combustion chamber. The engine control system comprises a first sensor that detects an intake pressure in the air intake device and generates a first sensor signal responsive to the intake pressure. A second sensor detects a state of the air regulator and generates a second sensor signal responsive to the state of the air regulator. A third sensor detects the engine speed and generates a third signal responsive to the engine speed. A control device operates in a first mode of operation when the intake pressure is varying to control an amount of fuel introduced by the fuel injector in response to the third sensor signal and the first sensor signal. The control device operates in a second mode of operation when the intake pressure is not varying to control the amount of fuel introduced by the fuel injector in response to the third sensor signal and the second sensor signal.
Another aspect of an embodiment in accordance with the present invention is an engine control system for an internal combustion engine for a marine drive. The engine comprises at least one combustion chamber that receives air-fuel charges. The engine operates at a variable engine speed in response to ignition of the air-fuel charges. The engine further comprises an air intake device that introduces air to the combustion chamber. The air intake device incorporates an air regulator (e.g., a throttle valve) that regulates an amount of air introduced to the combustion chamber by the air intake device. The air regulator has a variable state responsive to an actuator. A fuel injector introduces fuel to the combustion chamber. The engine control system comprises a first sensor that detects an intake pressure in the air intake device and generates a first sensor signal responsive to the intake pressure. A second sensor detects a state of the actuator of the air regulator and generates a second sensor signal responsive to the state of the actuator. A third sensor detects the engine speed and generates a third signal responsive to the engine speed. A control device operates in a first mode of operation when the intake pressure is varying to control an amount of fuel introduced by the fuel injector in response to the third sensor signal and the first sensor signal. The control device operates in a second mode of operation when the intake pressure is not varying to control the amount of fuel introduced by the fuel injector in response to the third sensor signal and the second sensor signal. In one embodiment in accordance with this aspect, the actuator is a cam that has a first surface at a variable distance from an axis of rotation and a second surface at a constant distance from the axis of rotation. The air regulator (e.g., the throttle valve) is coupled to the cam via a cam follower that follows the first surface during the first mode of operation and that follows the second surface during the second mode of operation. In another embodiment in accordance with this aspect, the actuator is a power control selector and the signal responsive to the state of the actuator is responsive to a power setting of the power control selector. The state of the air regulator (e.g., the position of the throttle valve) is responsive to changes in the power setting in the first mode of operation. The state of the air regulator is not responsive to changes in the power setting in the second mode of operation. Preferably, the air regulator in accordance with this embodiment is controlled by an electrical motor that operates to change the state of the air regulator (e.g., the position of the throttle valve) in response to changes in the power settings in the first mode of operation. The electrical motor maintains a constant state of the air regulator in the second mode of operation. In one particularly advantageous embodiment, the control device receives the signal responsive to the state of the actuator and generates control signals to the electrical motor to cause the electrical motor to change the state of the air regulator in response to the state of the actuator in the first mode of operation and generates control signals to the electrical motor to cause the electrical motor to maintain a substantially constant state of the air regulator in the second mode of operation.